In-Field Mummy Status

February is almost over, and in the field, about 40% of sclerotia assessed at the Botany & Plant Pathology Field Lab have germinated. That means with the right environmental conditions they’ll begin to infect the fields!

With the right environmental conditions, this mummy will produce an apothecium (fungal fruiting body, like a mushroom).

The best weather conditions for mushroom production include an average daily temperature of  ~45 Fahrenheit or higher, along with adequate rainfall. When this begins to happen in March, it’s a good idea to scout to find potential problem areas in your field. This may help you implement or tailor your IPM program.

For example, if you’ve already applied mulch in the fall, but choose to scout during March, you may find an area where the mulch has rinsed away from the winter rains. In this case, it may be beneficial to apply more mulch immediately in to cover apothecia and prevent spores from infecting the orchard.

We’re still collecting data regarding the timing of mulches and will report further after this field season. However, there has been suggestive evidence to show that mulching over these problem areas, as in the above example, can stop apothecia from growing through the mulch and reaching the soil surface. This is especially important for organic farmers, who need to utilize as many different tactics as possible to decrease disease incidence both for harvest this year, and decreasing sclerotia (or mummies) in the field the following fall and winter.

I’ve provided this Mummy Berry Scouting Video for anyone interested in learning to scout and wants an introduction to Mummy Berry.

Recent letter from a reader!

I’m working [on a] farm with perennial crops. I find your blog and research very interesting!

We have a ½ acre of highbush blueberries in their 7^th year of production. They are mulched with Douglas Fir sawdust covered with landscape fabric. I was wondering if you have recommendations on Mummy Berry control for our system… Do you think that leaving the landscaped fabric open during the berry drop, then restapling it over top of fallen berries would prevent any mummy berries from discharging ascospores in the spring? This might be less labour intensive than painstakingly removing all fallen berries by hand. Possibly. Given the ordeal of unstapling and restapling our plastic, hard to say. Anyways, was curious if you had any thoughts on this!

Response:  I’m glad you came across my blog!

I would not suggest pulling back the weed mat and allowing mummies to roll underneath, as I’ve seen this done on blueberry farms and the mummies ended up germinating under the weed mat, elongating until they reach a light gap, at which point they produce apothecia and sporulate.

Do you have raised beds or flat ground?

If you’re on flat ground, I might suggest simply sweeping up mummies
from the weed mat, collecting them, and disposing of them (you can
bury them in another area). If you’re on a raised bed, this might be
more difficult, as mummies tend to roll into the middle aisle. If this
is the case, sweeping them from the weed mat and raking the aisle may
be a good option (again, you’ll want to collect the mummies and
dispose of them). Also, keeping the grass cut and plant debris removed
from the middle aisle can help dry out any mummies that are left there.

Another option is to harvest the mummies. This can be time consuming,
but is very effective. Since my research doesn’t cover weed mat
operations at the present moment, I don’t have much information to
give you about that system. Hope this helped!

Here’s another resource that might come in handy for your other crops
too:

http://pnwhandbooks.org/plantdisease/blueberry-vaccinium-corymbosum-mummy-berry

As winter weather brings cooler temperatures, snowfall, and rains, mummies (or sclerotia) sit on the blueberry orchard floor accumulating degree days.

Rainfall and cooler temperatures are factors that influence the overwintering of M. vaccinii-corymbosi

As of November 2013, mummies in the field were already beginning to break dormancy and germinate.

Stipe initials are forming on overwintering mummy (sclerotium).

During December 2013, there were noticeably higher levels of germination and stipe initials were beginning to lengthen.

The blue arrows are pointing to a structure called a “stipe”. The stipe is the support for what will become an “apothecium” or fungal fruiting body, much like a mushroom cap. This picture is of a nearly-mature stipe and apothecium. However, in late-fall/early-winter, the beginning stages of stipe formation are visible on overwintering mummies in the field.

Most of the mummies found in the blueberry orchard can be found nestled under the leaf litter where they are less likely to dry out during periods of low rainfall.

The mummies generally fall from the bush in late-summer then are subsequently covered by fallen blueberry leaves.

Two rounds of mulching have now been applied to the experimental plots. Round One went out in late September when mummies still had their purple blueberry skin attached.

Round Two went out in mid-October after mummies had shed their purple blueberry skin.

It is unclear what function this removal of blueberry skin may have on the overwintering of the fungus, so it will be exciting to see if there are any differences in disease control efficacy.

In late-summer, mummies (sclerotia) still have purple/pink blueberry skin attached to the outer surface.

By early-fall, the blueberry skin is sloughed off, revealing dark colored mummies (sclerotia).

Round Three mulch is projected for mid-January. Pictures will follow.